title: Stability of a unitary Bose gas.
abstract: We study the stability of a thermal (39)K Bose gas across a broad Feshbach resonance, focusing on the unitary regime, where the scattering length a exceeds the thermal wavelength λ. We measure the general scaling laws relating the particle-loss and heating rates to the temperature, scattering length, and atom number. Both at unitarity and for positive a<<λ we find agreement with three-body theory. However, for a<0 and away from unitarity, we observe significant four-body decay. At unitarity, the three-body loss coefficient, L(3) proportional λ(4), is 3 times lower than the universal theoretical upper bound. This reduction is a consequence of species-specific Efimov physics and makes (39)K particularly promising for studies of many-body physics in a unitary Bose gas.
authors.affiliation: Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Fletcher
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Gaunt
authors.forename: Nir
authors.initials: N
authors.lastname: Navon
authors.forename: Robert P
authors.initials: RP
authors.lastname: Smith
authors.forename: Zoran
authors.initials: Z
authors.lastname: Hadzibabic